The use of sandblasting equipment to etch identifying markings on a hardened surface such as glass is well known. In particular, sandblasting equipment has been used in combination with an etching template in order to realize the desired marking. This technique has proven to be particularly useful in conjunction with the marking of glass articles such as windshields, side glass, and T-tops, as well as other parts of a car, thereby discouraging car thieves from stealing the "marked" car. The use of etched identification markings is also adaptable to household articles.
Self-contained sandblasting units have been disclosed. For example, U.S. Pat. No. 2,628,456 to Berg, U.S. Pat. No. 3,624,966 to Palmer, U.S. Pat. No. 4,048,918 to Peck, and U.S. Pat. No. 4,319,524 to Dunham et al. disclose sandblasting units capable of recycling abrasive material after it has contacted the etching surface. Recirculation of the abrasive particulate matter is desirable in order to obviate the uncontrolled scattering of abrasive material commonly associated with standard sandblasting techniques.
The optimal etching effect of a sandblasting unit is realized when the abrasive particulate material is directed perpendicularly to the etching surface. In this way, a deeper and more accurate groove or etch is created.